1. Field of the Invention
The present invention relates to a method for forming solder resist and a substrate for a package, and more particularly, to a method for forming solder resist and a substrate for a package that can differentiate a surface roughness of an inner chip mounting region from a surface roughness of an outer upper package mounting region.
2. Description of the Related Art
In manufacturing a circuit board, for example, a PCB, multiple layers of solder resist (SR) is formed according to the need. As can be seen from a package on package (PoP) substrate as a typical example, an SR thickness is small in a flip-chip mounting region or a controlled collapsed chip connect (C4) region but large in a PoP region. At this time, in an inner region including the C4 region, SR is opened in the shape of a fine peripheral bump, a bump on line (BOL), and a solder on pad (SOP), and in the PoP region, the SR is opened to be larger than the SOP of the C4 region. When performing packaging, chip attaching of the C4 region and package attaching of the PoP region are performed, respectively. Since underfill flow characteristics are different, it is needed to differentiate SR surface energy of the C4 region from SR surface energy of the PoP region. Further, in order to effectively perform underfill flow in the C4 region, it is not needed to open the SR up to an inner layer, but it is needed to open the SR slightly lower than a height of Cu as a circuit pattern.
FIGS. 2a to 2f are views schematically showing a conventional method for forming solder resist.
When forming 2-step SR 31 by the conventional method (refer to FIGS. 2a to 2d), it is difficult to differentiate SR surface energy of a C4 region from SR surface energy of a PoP region and properly fill the SR between Cu patterns 35. Although a plasma treatment etc. can be inserted in a process to differentiate SR surface energy, it is needed to overcome the problem of filling the SR between the Cu patterns 35.